It is known that an internal combustion engine of a motor vehicle is equipped with an aftertreatment system designed to change the composition of the exhaust gas in order to reduce the pollutant emissions. Some aftertreatment systems may include a particulate filter, for example a Diesel particulate filter (DPF) designed to trap diesel particulate matter or soot contained in the exhaust gas, and in particular a Catalyzed Diesel Particulate Filter (CDPF) having also a non-methane hydrocarbon oxidation function.
CDPF technology extends DPF technology by including an oxidation catalyst in association with a DPF. For example catalyzed diesel particulate filters have a filter media, i.e. a monolithic wall-flow substrate, coated with a catalyst in such a way to promote chemical reactions (i.e. oxidation reactions) among components of the exhaust gas, in particular non-methane hydrocarbons, at high temperatures. However, during the lifetime of the CDPF, the conversion efficiency of this component may not be constant but may decrease progressively due to ageing and/or poisoning effects. For this reason, it may happen that even if CDPF still traps the soot matter, its conversion efficiency may reach a level which makes it unsuitable to efficiently oxidize non-methane hydrocarbons, decreasing its contribution to the pollutant emission reduction.